Rheology,morphology, and crystallization behavior of melt‐mixed blends of polyamide6 and acrylonitrile‐butadiene‐styrene: Influence of reactive compatibilizer premixed with multiwall carbon nanotubes

Blends of polyamide6 (PA6) and acrylonitrile butadiene styrene (ABS) were prepared in presence or absence of up to 5 wt % of a reactive compatibilizer [styrene maleic anhydride copolymer (SMA) modified with 5 wt % multiwall carbon nanotubes (MWNT)] by melt‐mixing using conical twin screw microcompounder where the ABS content was varied from 20 to 50 wt %. The melt viscosity of the blends was significantly enhanced in presence of SMA modified by multiwall carbon nanotubes due to the reactive compatibilization, which leads to stabilized interphase in the blends. Furthermore, the presence of MWNT in the compatibilizer phase led to additional increase in viscosity and storage modulus. Morphological studies revealed the presence of either droplet‐dispersed or cocontinuous type depending on the blend compositions. Further, reactive compatibilization led to a significant change in the morphology, namely a structure refining, which was enhanced by MWNT presence as observed from SEM micrographs. DSC crystallization studies indicated a delayed crystallization response of PA6 in presence of ABS presumably due to high melt viscosity of ABS. The crystallization temperature and the degree of crystallinity were strongly dependent on the type of morphology and content of reactive compatibilizer, whereas the presence of MWNT had an additional influence. SAXS studies revealed the formation of thinner and less perfect crystallites of PA6 phase in the blends, which showed cocontinuous morphology. A unique observation of multiple scattering maxima at higher q region has been found in the blends of cocontinuous morphology, which was observed to be successively broadened in presence of the compatibilizer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Aqueous polymerization of acrylamide initiated by Ce(IV)-thiomalic acid redox system

Summary The use of a Ce (IV)-thiomalic acid (Ce⁴⁺-TMA) redox system as an initiator in the polymerization of acrylamide (M) in an aqueous medium has been investigated. The Ce⁴⁺ forms a 11 complex with TMA, decomposing through free radical mechanism in an acid medium. From 5 to 15% conversion the rate equation is where Rp is the rate of polymerization and x is 0.5 or 1.0 depending upon the concentration of monomer. The overall energy of activation has been calculated to be 9.12 k cal. deg^–1 mol^–1(38.12 kJ/mol) in the investigated range of temperature (25°–40°C) the degree of polymerization (P) of the polymer is directly proportional to [M]. The number of average molecular weight of the polymer remains unaffected at lower concentration of Ce⁴⁺ and is found to decrease at higher concentrations.In this investigation the kinetics and mechanism of the Ce(IV)-thiomalic acid (TMA) redox system to initiate the polymerization of acrylamide has been studied.Acrylamide (E. Merck) was purified by usual methods. Thiomalic acid and eerie ammonium sulfate were used without purification. All solutions were p repared in twice distilled water.The polymerization procedure adopted was similar to the one used by MISRA et al. [3, 4]. The polymerization was followed by quantitative estimation of the double bonds in acrylamide as described [8]. A small variable induction period was observed perhaps due tothe residual oxygen in the thiol solution. Curves were plotted after eliminating the induction period.The average molecular weights of the p olymers were determined by viscosity measurements at 30°C in an aqueous medium using the relationship of DAINTON et al. [2]. Where []=intrinsic viscosity of the polymer solution and ¯Mn=molecular weight of the sample.     

Grafting onto wool. VII. Ceric ion-initiated graft copolymerization of vinyl monomers. Comparison of monomer reactivities

In an attempt to compare relative reactivities of vinyl monomers toward grafting, methyl methacrylate (MMA) and acrylic acid (AAc) were grafted separately to Himachali wool in aqueous medium by using ceric ammonium nitrate (CAN) as redox initiator. Nitric acid was found to catalyze the reaction. Percent grafting was determined as a function of concentration of nitric acid, concentration of CAN, concentration of monomer, time, and temperature. Optimum conditions for maximum grafting were evaluated for each monomer and were found to depend upon the nature of the monomer. Reactivities of MMA and AAc toward grafting were compared with those of methyl acrylate (MA), ethyl acrylate (EA), and vinyl acetate (VAc) reported earlier from this laboratory and were found to follow the order MA > EA > MMA > VAc > AAc. An explanation for the observed order of reactivity of different vinyl monomers is presented.     

A novel approach towards molecular memory device in gate tunable structure of MoS2-graphene

Molecular interaction in two-dimensional(2D)van der Waals(vdW)interfaces has drawn tremendous attention for extraordinary materials characteristics.Sofar sensing characteristics of molecular interaction has been exploited extensively to reach the detection limit to a few parts-per-billion(ppb)of molecules and far less attention is given to the evolution of persistent current state due to the molecular exposure.Our study focuses on molecular memory operation of MoS₂-graphene heterostructure based field effect transistor.Metastable resistance state of the device due to the external perturbation of molecules is tuned to get a nearly relaxation free current state at much lower molecular concentration of 10 ppb tofacilitate non-volatile memory features for molecular memory operation.An ultrafast switching operation in milli-second order is achieved at room temperature for the fastest recovery obtained sofar in any molecular sensor.The process is co-controlled both by molecular as well as external charge density.     

Failure Analysis of Stacker-cum-Reclaimer in Ore Handling Plant

A catastrophic failure of a Stacker-cum-Reclaimer led to loss of several days of service in one ore handling plant in India. The failure was severe enough to initiate an investigation into the possible causes of failure and estimation of the residual life for other units of Stacker-cum-Reclaimer of the same design and age, working in the plant. The failure analysis included a visual inspection of the failed structure, metallographic studies, static stress and stability analysis under normal operating conditions, stress analysis for a possible impact load on the structure, experimental stress analysis, and fatigue life cycle analysis. The results obtained indicate that the failure could be caused by an impact load arising out of some operational conditions resulting from the conditions of the rail track on which the machine travels. The material properties, the physical conditions of the material, and a fatigue analysis indicate that the existing system can work for several more decades, provided some checkpoints are planned and instituted to monitor the health of the structure at regular intervals.     

Nitrogen and hydrogen related infrared absorption in CVD diamond films

In this paper, we investigate on the presence of hydrogen and nitrogen related infrared absorptions in chemical vapour deposited (CVD) diamond films. Investigations were carried out in cross sections of diamond windows, deposited using hot filament CVD (HFCVD). The results of Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) and Raman spectroscopy carried out in a cross section of self-standing diamond sheets are presented. The FTIR spectra showed several features that have not been reported before. In order to confirm the frequency of nitrogen related vibrations, ab-initio calculations were carried out using GAMESS program. The investigations showed the presence of several C-N related peaks in one-phonon (1000-1333 cm^− 1). The deconvolution of the spectra in the three-phonon region (2700-3150 cm^− 1) also showed a number of vibration modes corresponding to sp^mCH_n phase of carbon. Elastic recoil detection analysis (ERDA) was employed to compare the H content measured using FTIR technique. Using these measurements we point out that the oscillator strength of the different IR modes varies depending upon the structure and H content of CVD diamond sheets.     

Feasibility of an immunoassay for mevalonolactone

Trace eyeblink classical conditioning was assessed in patients with bilateral medial-temporal amnesia and matched control participants who had previously shown equivalent delay eyeblink conditioning (J. D. E. Gabrieli et al., 1995). The silent trace interval varied for durations of 500, 750, or 1,000 ms in successive sessions separated by at least 2 weeks; extinction trials followed each session. Patients with amnesia produced significantly fewer conditioned responses (CRs) than did control participants at all trace intervals. Both groups produced fewer CRs as the trace interval lengthened. Thus, the temporal lobe memory system in humans makes an essential contribution to normal acquisition in trace, but not delay, classical eyeblink conditioning.     

Endosonographic evaluation of the rectum in children with extrahepatic portal venous obstruction

OBJECTIVE: To determine the mechanism of the adverse relationship between perioperative blood transfusion and lung cancer recurrence, by focusing on endothelial cell adhesion molecules (CAMs), which are thought to play a role in distant tumor cell implantation. DESIGN AND OUTCOME MEASURES: Murine endothelial cells were cocultured with allogeneic leukocytes, syngeneic leukocytes, and syngeneic lung carcinoma cells for 60 hours. The percentage of endothelial cells expressing vascular CAMs (VCAMs) and intercellular CAMs (ICAMs) was quantified during this time using indirect immunofluorescence and flow cytometry. Tumor cell adhesion to the endothelium was quantified for 6 hours using cells labeled with sulfur 35 and a scintillation counter. SETTING: Laboratory. MATERIALS: C57/BL and Balb/C mice. RESULTS: Vascular CAM was not expressed on the endothelium, but ICAM was preferentially expressed without stimulation. Tumor-cell adhesion and endothelial ICAM expression were inversely related. After 15 hours of coculture, tumor cell adhesion was four-fold greater in the experimental group than in the control, and coincident endothelial ICAM expression was fourfold lower. CONCLUSION: Endothelial cell ICAM expression is negatively correlated with metastatic potential.